Coaxial line termination



Oct. 15, 1946. J. w. TILEY COAXIAL LINE TERMINATION Filed April 28, 1944 INVENTOR. 1 Ri 9 Patented Oct. 15, 1946 COAXIAL LINE TERMINATION John W. Tiley, Philadelphia Pa., assignor to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application April 28, 1944, Serial No. 533,231

7 Claims. 1

The present invention relates to coaxial line terminations and more particularly to a coaxial line termination whichis adapted to receive energy from a coaxial line under test so that the energy may be dissipated in the form of heat.

In the testing of ultra, high frequency equipment it frequently is necessary to test coaxial lines or conductors and equipment connected thereto. For such testing purposes it is desired to have a coaxial line termination which will absorb energy from-the coaxial transmission line without producing any substantial degree of reflection back on the line and which will disi-. pate the received energy in a difierent form, as for instance in the form of heat. A termination of the type should be relatively stable for changes in humidity and temperature so that the standing wave ratio of the termination undergoes no substantial change. Heretofore terminations have been devised which, however, have had the disadvantage of being variable in their characteristics in response to changes in temperature and changes in humidity.

In accordance with the present invention the coaxial line termination is provided which utilizes a dielectric impedance device so constructed and arranged as to produce no substantial reflection of incident energy back on the coaxial transmission line to which the device is connected. The dielectric medium utilized in such coaxial line termination preferably is one which has a relatively high radio frequency loss characteristic so that energy received is transformed or translated into heat.

It, therefore, is an object of the present invention to provide an improved coaxial cable or transmission line termination which will dissipate energy received from a coaxial cable or transmission line.

Another object of the present invention is to provide an improved coaxial transmission line termination which has relatively stable charac teristics although the temperature and humidity conditions may be varied.

It is still another object of the present invention to provide an improved method of constructing a coaxial line termination.

Other and further objects of the present in- .2 of the termination broken away to expose the interior structure;

Figure 2 is a view of a portion of the coaxial line termination sown in Figure 1; and

Figure 3 is a rather diagrammatic representation of another manner in which the coaxial line termination may be constructed in its interior.

A coaxial line termination constructed in accordance with the present invention preferably includes a cylindrical outer conductor ll having adjacent one end a female connector of the type generally utilized for interconnecting coaxial line sections. The other end of the outer conductor H may be reinforced by a reinforcing ring 13. At spaced apart points along the outer surface of the outer conductor ll there are positioned a plurality of radiating fins I which may be stamped out of circular or rectangular metal sheets having apertures therein so that the fins vention subsequently will become apparent by reference to the following description taken in connection with the accompanying drawing wherein Figure 1 is a view of a coaxial cable termination constructed in accordance with the present invention, and wherein the view shows a portion It may be fitted over the exteriorot the outer conductor ll. Preferably the radiating fins H are then suitably soldered so as to retain the fins in position and to insure a good heat conductive connection between the fins and the outer surface of the outer conductor II. On the inside of the conductor ll there is arranged a device shown in Figure 2 which comprises an inner conductor l5 having adjacent one end a recessed portion I6 adapted to receive a portion of the end of the conductor of acoaxial line to which the device is to be attached by the connector l2. The inner conductor I5 extends the full length of the outer conductor I I and is supported in coaxial position by a member ll having a cylindrical portion l8 and a conical portion IS. The cylindrical portion [8 is substantially equal to the inner diameter of the outer conductor H, and the conical portion l9 has a taper so selected that the incident energy impinging upon the tapered portion will not be reflected in any substantial degree back toward the coaxial cable or transmission line to which the device is to be connected. The member I! has a coaxial bore slightly larger than the diameter of the inner conductor IS. The member I1 is cemented in position on the inner conductor 15.

The member I! mounted on the inner conductor 15 is made of a dielectric material which has a high loss characteristic at ultra high frequencies and which, however, exhibits no appreciable change in other characteristics due to temperature or humidity variations. formed of a ceramic mix composed of conventional clay, steatite, and the like mixed with a certain percentage of a resistive substance in The device may be 3 finely divided state; Such resistive substances may comprise silicon carbide, carbon black, colloidally suspended defiocculated graphite and' the like. Where the device I1 is in the form of a ceramic member the device is cemented to the inner conductor and is also cemented over its cylindrical portion It! to the outer conductor by a cement which may comprise fifty per cent ball clay and fifty per cent lamp black by volume mixed into a thin paste with a solution of fifty per cent water and fifty per cent sodium metasilicate or water glass by volume.

Other dielectric materials also may be used such'as a synthetic resin or plastic material containing particles of resistance substances so that the material will exhiibt a high loss characteristic at ultra high frequencies. Such material also should be cemented to the inner and outer conductors so as to give the best possible heat conductive relation between the parts.

In Figure 3 is shown another manner in which the inner conductor l5 may be provided with a dielectric device 2| which is in the form of a cylindrical section. This dielectric device 2| may be formed of materials similar to those suggested for the device ll of Figures 1 and 2. In order that the energy receiving and dissipating device 2| may not reflect energy back toward the line to which the device is to be connected a quarter wave matching transformer 22 may be interposed between the inner conductor l5 and the dielectric device 2|. The outer conductor ll therefore should be provided with sufllcient radiating fins or surfaces for a distance extending somewhat beyond the left hand end of the dielectric body 2| so that adequate radiation surface is provided.

While for the purpose of illustration and description of the present invention certain specific embodiments have been shown in the drawing it is to be understood that it is not to be limited thereto since obviously the invention is susceptible of other embodiments commensurate with the scope of the invention as defined in the appended claims.

This invenion is hereby claimed as follows:

1. A termination device for a coaxial line, comprising inner and outer coaxial conductors, a

dielectric body interposed between said conductors, said body being formed of a ceramic composition containing finely divided particles of resistive material, said body being cemented to said inner and outer conductors so as to be in good heat conductive relation thereto, means for preventing substantial reflection of incident ultra high frequency energy by said body and heat radiating fins for cooling said outer conductor.

-2. A termination for a coaxial transmission line, comprising inner and outer coaxial conductors, a dielectric member mounted adjacent said conductors, said member being arranged in good heat conductive relation to said conductors, means for preventing the reflection of incident ultra high frequency energy by said member, and

heat radiating fins mounted on said outer conducton,

3. A termination for a coaxial transmission line, comprising inner and outer coaxial conductors, a

5 dielectric member mounted adjacent said conductors, said member being formed of a material having a high loss characteristic at ultra high frequencies, said member having a cylindrical portion and a tapered portion, said cylindrical portion being arranged in good heat conductive relation to both said conductors, said tapered portion being arranged to minimize reflection of incident ultra high frequency energy, and means for dissipating the heat generated by said member.

4. A termination for a coaxial transmission line, comprising inner and outer coaxial conductors, a dielectric member mounted on said inner conductor, said member being formed of a ceramic material having a high loss characteristic at ultra high frequencies and having relatively small changes in other characteristics in response to humidity and temperature variations, said member having a cylindrical portion and a tapered portion, said tapered portion being arranged to minimize reflection of incident ultra high frequency energy, said cylindrical portion being cemented to said inner and said outer conductors so as to be in good heat conductive relation thereto, and heat radiating fins mounted on said outer conductor for dissipating heat generated by said dielectric member.

5. A termination for a coaxial transmission line, comprising inner and outer coaxial conductors, a dielectric member arranged to receive ultra high frequency energy from said conductors, said member being formed of a material having a high loss characteristic at ultra high frequencies, said member being in good heat conductive relation 40 to at least one of said conductors, said member having portions of diiferent diameters for preventing substantial reflection of incident ultra high frequency energy by said member, and heat radiating means associated with said one conductor for dissipating heat energy from said member.

6. In a device of the class described, a hollow conductor, a dielectric member within said conductor in heat conducting relation thereto, said member being formed of a material having a high loss characteristic at ultra high frequencies, and heat radiating means on said conductor for dissipating heat energy from said member.

7. In a device of the class described, a hollow conductor, a dielectric member within said conductor in heat conducting relation thereto, said member being formed of a material having a high loss characteristic at ultra high frequencies, means for minimizing reflection of incident ultra high frequency energy by said member, and heat radiating means on said conductor for dissipating heat energy from said member.

JOHN W. TILEY. 

